| Summary: | 碩士 === 崑山科技大學 === 電子工程研究所 === 93 === The microstructures and the microwave dielectric properties of NiNb2O6(NN) and CaNb2O6(CN) ceramics with different amount of CuO addition prepared by a reaction-sintering process were investigated and analyzed. In this process, the mixture of raw materials was sintered directly without any calcination stage involved. Pure NN and CN columbite phase can be obtained by the reaction-sintering process. The sintering temperature for NN and CN ceramics with CuO addition could effectively lowered about 200oC~300oC. The shrinkage and density of NN ceramics are lower when mixed 50% NiO + 50% Ni(NO3)2 and Nb2O5. As NiO was mixed with Nb2O5, higher shrinkage and density was obtained. NN ceramic of density 5.51g/cm3 (97.66% of theoretic value) was obtained at 1300oC for 2 h sintering. CN ceramic of density 4.37g/cm3 (92.02% of theoretic value) was obtained at 1420oC for 2 h sintering. After 1300oC/2h sintering, NN ceramics exhibt excellent microwave dielectric properties：εr = 20.7, a Q×f value of 20,000(at 9GHz) and τf =-31.9ppm/oC. The τf value of NN- TiO2 ceramic changed from a negative value for NN to a positive value. After 1250oC/2h sintering, NT3 ceramics with εr=44.9, a Q×f value of 7700(at 6GHz) and τf=72ppm/oC were obtained. CN ceramics with εr=14.9, a Q×f value of ~23000(at 11GHz) and τf =-23.1ppm/oC were prepared after sintered at 1420oC for 2 h.
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